Field of the Invention
The invention relates to a security chassis for a secure area in the interior of a security housing. The configuration has a supporting frame for the printing mechanism in the non-secure area, a printing module being arranged such that it can move in the supporting frame and being protected mechanically against unauthorized access. The invention is suitable for devices which have an internal secure area and from which excess heat is to be dissipated. It is used in particular in franking machines, addressing machines and other mail-processing devices.
A thermal transfer franking machine distributed by Francotyp-Postalia of Germany, the assignee of this application, under the designation T1000 has a thermal transfer print head arranged permanently in the housing for printing a franking stamp. The franking stamp contains postal information previously entered and stored, including the postal charge data for the carriage of the letter. A compartment fitted to the housing is used to accommodate a replaceable ink-ribbon cassette (U.S. Pat. No. 4,767,228). While a door leading to the compartment can be opened at any time, access to the secure area of the printing device is prevented by a security housing.
If a franking machine is to be opened for repair purposes, break-off screws belonging to the security housing have to be destroyed. In franking machines and other mail-processing devices having a security housing, lead seals or plastic parts may additionally be used as a further protection against access to the microprocessor controller and to the control lines of the stationary print head. Following a repair which requires the security housing to be opened, break-off screws belonging to the security housing, lead seals or the plastic parts serving to prevent access must be replaced.
The JetMail(copyright) franking machine of Francotyp-Postalia is equipped with a base and a removable meter. Only the latter is protected against misuse by an appropriately designed housing. As distinct from this, the housing of the base, which contains a mail transport device and an inkjet printing device, does not have to have any protective function and can be of repair-friendly design. Since the ink reservoir of the print head is arranged separately and can be replaced, replacement of the print head is dispensed with. In addition, no special security measures for the print head or to protect the drive and data signals have to be taken if, using a specific piezoelectric inkjet print head, a security stamp with a mark is printed which permits rechecking of the authenticity of the security stamp (U.S. Pat. No. 6,041,704).
Inkjet print heads have also already been used in the printing module in franking machines having a security housing, that is to say without a separate housing for base and separable meter (for example, in mymail(copyright) of Francotyp-Postalia, in Personal Post(trademark) of Pitney Bowes, and the PortoStar of Neopost). An ink reservoir and a bubble jet print head are integrated into a replaceable ink cartridge, as previously known, for example, from the half-inch ink cartridges of Hewlett Packard. However, it must be possible for a hatch in the security housing to be opened by the user in order to remove or replace an empty ink cartridge. Because of the access to the printing mechanism which is therefore made possible and, possibly, to the printer electronics or making contact with the ink cartridge, the result may be new possibilities for producing an unauthentic security stamp. Some postal authorities place strict requirements on the approval of franking machines, which makes their producers equip such ink cartridges with additional security means or take suitable protective measures, so that influence can be exerted neither indirectly via manipulated ink cartridges or directly on the printing operation in order to print franking stamps without paying for them.
In addition to the purely electronic solutions, solutions are already known which mechanically prevent a further printing device being controlled impermissibly with the printing data during the printing operation. According to U.S. Pat. No. 6,102,534 or published European patent application EP 875 861 A2, a franking machine for franking printing can be operated only when a hatch is closed. However, the hatch must continue to be open in order to remove or replace an empty ink cartridge. A secure area in the interior of the device housing is not particularly protected in any of the aforementioned solutions.
European patent application EP 1 024 682 A2 discloses a security housing which comprises two housing shells, their side walls overlapping one another in the assembled state. The two housing shells enclose the inner secure area having a circuit board on which a controller is constructed. However, no dissipation of heat by means of forced convection is provided. However, if ventilation slots were to be provided for heat dissipation, then the inner area would either have to be viewed as no longer secured or the production costs of the housing shells would become unacceptably high.
However, the user of a franking machine is to continue to be provided with the possibility of removing or replacing an ink cartridge without there being a possibility for manipulation through an opening required for this purpose, in order to penetrate into the inner secure area.
It is accordingly an object of the invention to provide a security chassis, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a housing construction with internal chassis parts that cover the inner secure area and permit heat dissipation by means of forced convection of the air stream to the outside, with low production costs.
With the foregoing and other objects in view there is provided, in accordance with the invention, a security chassis for the secure area in the interior of the security housing, the security housing having an interior with a secure area and a non-secure area and a printing mechanism disposed therein. The configuration comprises:
at least two mutually spaced-apart chassis shells enclosing the secure area, one of the chassis shells having a functional edge;
a supporting frame for the printing mechanism in the non-secure area supported on the functional edge of the one chassis shell, and a printing module movably disposed in the supporting frame and protected mechanically against unauthorized access;
the functional edge having ventilation openings formed in a margin thereof, the margin of the functional edge and the ventilation openings having a geometric shape rendering penetration of tools into the secure area enclosed by the at least two chassis shells substantially impossible.
In accordance with an added feature of the invention, the ventilation openings at the margin of the functional edges are formed in mutually offset rows.
In accordance with an additional feature of the invention, the chassis shells include a first chassis shell having an edge formed with ventilation openings and a second chassis shell spaced apart from the first chassis shell formed with ventilation openings at the margin of the functional edges thereof.
In accordance with another feature of the invention, the margins of the chassis shells wrap around one another and are shaped at an angle rendering impossible a penetration of tools.
In accordance with a further feature of the invention, at least one of the functional edges is configured in an L shape.
In accordance with again a further feature of the invention, at least one of the functional edges of at least one of the chassis shells is configured in a U shape or an inverted U shape.
In accordance with a concomitant feature of the invention, the offset between the rows is configured only to render impossible a penetration of tools into the secure area along a rectilinear path.
In other words, inside the security housing there is at least one secure area and at least one non-secure area. Only authorized persons, such as service engineers, are authorized to make access to both areas and may open the security housing. By means of a housing construction with internal chassis parts, the secure area in the interior of the security housing is protected against unauthorized access. At least two chassis shells spaced apart from each other surround the secure area. A supporting frame for the printing mechanism in the non-secure area is supported on at least one functional edge of at least one chassis shell. A printing module is arranged such that it can move in the supporting frame and is protected mechanically against unauthorized access. In this case, the starting point is the thought that the mutually spaced functional edges have ventilation openings formed at their edge, the geometric shape of the edge of the functional edges making penetration of tools into the secure area enclosed by the two chassis shells impossible. Provision is made for the ventilation openings at the edge of the functional edges to be arranged in the form of mutually offset rows, the offset being only such that penetration of tools into the secure area on a rectilinear path is made impossible. Ventilation openings are arranged at the edge of a first chassis shell and at the edge of functional edges of a second chassis shell spaced apart from the first. The edges of the chassis shells, which wrap around each other, are, at the same time, shaped at an angle which makes penetration of tools impossible, at least one of the functional edges of at least one of the chassis shells being configured in a U shape or in an inverted ∩ shape or L shape. As a result of this design, the weight and the forces acting in the printing mechanism are dissipated via the supporting frame onto the upper chassis shell and from the latter via the lower chassis shell onto the lower housing part. The printing mechanism is advantageously easily accessible for service and for the ink cartridge change, and good dissipation of heat is ensured, nevertheless chassis parts cover the inner secure area.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a security chassis, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.